【例3-4】求后序遍历

#include<iostream>
#include<cstdio>
#include<cstring>
#include<vector>
#include <algorithm>
using namespace std;
vector <char> pre,in,post;
int i;
void rec(int l,int r)
{
    if(l>=r)return ;
    int m=distance(in.begin(),find(in.begin(), in.end(), pre[i++]));    
    rec(l,m);
    rec(m+1,r);
    post.push_back(in[m]);
}
int main()
{
    string s1,s2;
    cin>>s1>>s2;
    for(int i=0;i<s1.size();i++)
        pre.push_back(s1[i]);
    for(int i=0;i<s2.size();i++)
        in.push_back(s2[i]);
    rec(0,s1.size());
    for(int i=0;i<post.size();i++)
        printf("%c",post[i]);
    cout<<endl;
}